Tru-Tone bulbs operate at standard US single-phase voltage (110V AC) and use standard base sizes:
E12 or Candelabra Base for our C7 bulbs
E17 or Intermediate Base for our C9 bulbs
E26 or Medium Base for our S14 bulbs
Our bulbs will work in most standard sockets of the correct size and voltage.
We have encountered some light strings, sold as a set with bulbs, that have non-standard E12 or E17 sockets made to fit the bulbs they are sold with. These may have a more narrow flare at the top of the socket that prevents Tru-Tone bulbs from screwing all the way in, as shown in the image below:
If you are still unsure about your light string, please reach out to our customer support and include a close-up picture of one of the sockets on your string. We should be able to determine whether or not it is compatible with our bulbs.